Jetlag and Melatonin
What is melatonin, when is it secreted and where from?
Melatonin is a hormone that acts as a back up zeitgeber for the body clock to entrain the master clock in the SCN. It is secreted from the pineal gland at night due to light inhibiting its synthesis. It is important for regulation of the circadian rhythm.
What are the effects of shift work on the circadian rhythm?
Shift work is another form of social jetlag that disrupts the circadian rhythm and leads to irregular and shortened sleep. This has consequences for human health and is associated with increased risk of CVD, diabetes, obesity and cancer.
What are some health problems associated with disordered rhythms?
Sleep deprivation, Poor alertness, increased risk of accidents, mood problems, increased risk of heart disease, cancer, obesity and alzhiemers disease
What health problems are associated with social jetlag?
Studies show that with increased numers of SJ hours, a person has increased risk of increased waist circumference, increased BMI, increase fat mass and increased obesity and metabolic syndrome.
What happens to the melatonin profile when you travel east or west?
The melatonin profile takes about 92m/day to adjust when travelling west and 52 min per day when travelling east. This means that initially when you travel your melatonin profile stays the same, despite the change in your sleeping pattern
Define jetlag. Explain what it does
This is a physiological condition which results from alterations to the body's circadian rhythms resulting from rapid long-distance trans-meridian travel on a high speed aircraft. This leads to either a phase delay or advance of the body clock, desynchronising it from the rhythm generated by the master clock in the SCN. This will have behavioural, autonomic or endocrine effects as the peripheral clocks also become desynchronised.
What is social jetlag?
This is the discrepency between internal and external time. It is the difference between mid-sleep during a work week and mid-sleep during free days.
How would you treat jetlag when travelling east and west with light exposure?
When travelling east you want to administer light in mornings and block light in the evenings. This is because that melatonin profile in lagging and will occur earlier in the mornings to the afternoon. Administering light in the morning therefore advances the clock. When travelling west you want to administer light in the evenings and block light in the mornings . This is because the melatonin profile is advanced and will start early afternoon and end early morning. By administering light in the evenings you delay the clock.
How would you treat jetlag when travelling east and west with melatonin treatment?
When travelling east you would administer melatonin in the evenings, before bed to advance the profile from morning to evening. When travelling west you would administer melatonin in the early morning to delay the profile from early morning to late.
What reset to the body clock would you want when travelling east or west in order to shift the melatonin profile back to normal?
Would want to phase delay the clock when travelling west to move the melatonin profile to the right. Would want to phase advance the clock when travelling east and shift the profile to the left
What are the benefits of melatonin, describe the late night hypothesis
melatonin is a very powerful anti-oxidant. The late at night hypothesis suggests that disruption to melatonin secretion as a result of shift work of blue light exposure (devices) leads to loss of the beneficial antioxidant effects of melatonin leading to shift-work related pathologies (CVD, diabetes, obesity, cancer)